The present invention relates to a miter saw for cutting a workpiece placed on a base by vertically swinging a rotary tool such as a circular saw located above a turn table or sliding the rotary tool in a radial direction of the turn table.
Such a miter saw has a normal cutting function such that a cutting tool is vertically swung to cut a workpiece and also has an additional push-cutting or draw-cutting function such that the cutting tool is moved horizontally to push-cut or draw-cut the workpiece. Such an additional cutting function is often carried out as well as the normal cutting function.
An example of this type miter saw is disclosed in U.S. Pat. No. 4,537,105, wherein a guide bar retaining member is provided on the turn table, and a guide bar is vertically swingable through a spring by the guide bar retaining member. A motor and a gear case provided with the cutting tool is horizontally movable along the guide bar. In cutting a wide workpiece by moving or expanding the gear case having the cutting tool, a center distance between the cutting tool and a pivotal hinge portion is long, so that a large load is applied to the spring at the pivotal hinge portion, and the cutting tool cannot be retained by the spring. If a spring force of the spring is set to be strong so as to retain the cutting tool under the expanded condition of the gear case, the spring force will become too large to conduct a cutting operation under a short condition of the gear case, with the result that a large force for depressing a handle is required to reduce the operability.
To solve this problem, there has been developed a technique for making a change in spring force of the spring regardless of a moving distance of the cutting tool by sliding the cutting tool for the cutting operation of a wide workpiece and moving the pivotal hinge portion (Japanese Utility Model Laid-open Publication No. 62-11526). In this technique, a turn table is mounted on a base for placing a workpiece thereon, and a guide bar retaining member is provided on the turn table. A guide bar is retained by the guide bar retaining member in such a manner as to be located above the turn table and be horizontally movable. An arm is pivotably mounted to an end of the guide bar, and a cutting tool such as a circular saw or a grinding stone and a motor for driving the cutting tool are mounted to the arm. Thus, the cutting tool located above the turn table is vertically swung with the arm, or is horizontally moved to carry out various cutting operations with respect to the workpiece placed on the base.
However, as mentioned above, the guide bar retaining member is provided on the turn table, and the guide bar is horizontally movably supported by the guide bar retaining member. Furthermore, the cutting tool and the motor is vertically swingably mounted to the end of the guide bar. Accordingly, an overall load of a cutting tool unit including the guide bar, the cutting tool, the motor, etc. is applied to only a supporting portion of the guide bar to the guide bar retaining member. As a result, in the push-cutting or draw-cutting operation, a load application point of the cutting tool unit is located away from the supporting portion, and a large moment is generated at the supporting portion. This moment causes a defect that "tangling" tends to occur at the supporting portion to hinder smooth movement of the guide bar and possible adverse effect to the cutting operation. Accordingly, it is actually necessary to cope with this "tangling" by providing different supporting means at the supporting portion of the guide bar.